This invention relates to apparatus and methods for chemical mechanical polishing and cleaning a substrate in an integrated system.
An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive or insulative layers on a silicon wafer. After each layer is deposited, it is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the outer or uppermost surface of the substrate, i.e., the exposed surface of the substrate, becomes increasingly non-planar. This non-planar surface presents problems in the photolithographic steps of the integrated circuit fabrication process. Therefore, there is a need to periodically planarize the substrate surface.
Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is placed against a rotating polishing pad. The polishing pad may be either a xe2x80x9cstandardxe2x80x9d pad or a fixed-abrasive pad. A standard pad has a durable roughened surface, whereas a fixed-abrasive pad has abrasive particles held in a containment media. The carrier head provides a controllable load, i.e., pressure, on the substrate to push it against the polishing pad. A polishing slurry, including at least one chemically-reactive agent, and abrasive particles if a standard pad is used, is supplied to the surface of the polishing pad.
After the substrate has been polished, it is typically cleaned, e.g., by a brush scrubber or megasonic cleaner, to remove excess slurry, polishing chemistry and other debris from the polishing process. After cleaning, the substrate is dried, e.g., by a spin-rinse drier, for return to the clean room. In some systems, e.g., systems that use the Marangoni effect, the cleaning and drying functions can be combined. Unfortunately, even after cleaning and drying, particles and other defects may remain on the substrate surface.
The chemical mechanical polishing and cleaning devices can be constructed as an integrated system with a single front-end automation interface between the clean room and the polishing and cleaning systems. An example of such an integrated system is the Mirra Mesa(trademark) chemical mechanical polishing system from Applied Materials, Inc. of Santa Clara, Calif. Such an integrated system can include multiple ports to receive multiple cassettes at the interface with the clean room. Unfortunately, transport of the substrates between the cassettes and the polisher and cleaner can occasionally become backlogged, leading to a decrease in throughput.
In one aspect, the invention is directed to a substrate processing system. The system has a factory interface module, a chemical mechanical polisher, and a substrate transfer system. The factory interface module includes a chamber, a plurality of cassette supports to support a plurality of cassettes outside the chamber, a plurality of ports for the transfer of substrates between the cassettes and the chamber, and a storage station located in the chamber to hold a plurality of substrates. The substrate transfer system transports a substrate through the chamber between the cassettes, the storage station and the polisher.
Implementations of the invention may include one or more of the following features. The storage station may hold the substrates in a substantially horizontal position. The storage station may includes a plurality of opposing slots to secure the edges of the substrates. The storage station may hold a pad break-in wafer or a monitor wafer. A controller may cause the substrate transfer system to transport the break-in wafer to the chemical mechanical polisher and to cause the polisher to break in a polishing pad with the pad break-in wafer. The pad break-in wafer may be a quartz wafer. They system may include a cleaner and/or a defect monitor. The defect monitor may have a port coupled to the factory interface module. A controller may cause the substrate transfer system to transport the monitor wafer to the polisher, cause the polisher to polish the monitor wafer, transport the polished monitor wafer to the cleaner, and cause the substrate transfer system to transfer the monitor wafer from the cleaner to the defect monitor. An input station may hold at least one substrate for loading into one of the chemical mechanical polisher and cleaner. The substrate transfer system may include a first robot to transport a substrate between the cassettes, the storage station and the input station, and a second robot to transport the substrate between the input station and the chemical mechanical polisher.
In another aspect, the invention is directed to a substrate processing system that has a factory interface module, a chemical mechanical polisher, a cleaner, a defect monitor, and a substrate transfer system. The factory interface module has a plurality of ports to receive a substrate from one of a plurality of cassettes in a clean room. The defect monitor detects defects on the substrate following polishing and cleaning at the polisher and cleaner. The substrate transfer system transports the substrate between the cassettes, the polisher, the cleaner, and the defect monitor. The factory interface module, polisher, cleaner, and defect monitor are disposed to form an integrated system.
Implementations of the invention may include one or more of the following features. The defect monitor may have a port coupled to the factory interface module. The defect monitor may measure a plurality of defect parameters, such as a number and size distribution of particles or scratches. A controller may receive a plurality of defect parameters from the defect monitor. The controller may be configured to determine whether one or more defect parameters meet a first criteria and to stop transferring substrates into the polisher if the first criteria is met. The controller may be configured to determine whether one or more defect parameters meet a second criteria, and to increase the number of substrates sent to the defect monitor if the second criteria is met. The factory interface module may include a storage station to hold a plurality of substrates, e.g., at least one monitor wafer. A controller may cause the substrate transfer system to transport the monitor wafer to the polisher, cause the polisher to polish the monitor wafer, transfer the polished monitor wafer to the cleaner, and cause the substrate transfer system to transport the monitor wafer from the cleaner to the defect monitor if the first criteria is met. An input station may hold at least one substrate for loading into one of the chemical mechanical polisher and cleaner, and the substrate transfer system may include a first robot to transport the substrate between the cassettes, the defect monitor and the input station, and a second robot to transport the substrate between the input station and the chemical mechanical polisher.
In another aspect, the invention is directed to a method of processing a substrate. In the method a first substrate is transferred from a storage station in a factory interface module to a polisher, a polishing pad at the polisher is broken in with the first substrate, and the first substrate is returned to the storage station. A second substrate is transferred from a cassette through the factory interface module to the polisher, and the second substrate is polished, cleaned and returned to the cassette.
In another aspect, the invention is directed to a method of processing a substrate. In the method, a substrate is transferred from a cassette through a factory interface module to a polisher, the substrate is polished at a chemical mechanical polisher and cleaned at a cleaner, and the substrate is transferred from the cleaner through the factory interface module to a defect monitor. A defect parameter is measured with the defect monitor, and the substrate is returned to the cassette.
In another aspect, the invention is directed to a method of processing substrates in which a first substrate is transferred from a cassette through a factory interface module to a polisher, polished at chemical mechanical polisher, and cleaned at a cleaner. A second substrate is transferred from a storage station in the factory interface module to the polisher, polished at the polisher, cleaned at the cleaner, and transferred from the cleaner through the factory interface module to a defect monitor. A defect parameter of the second substrate is measured with the defect monitor, and a polishing parameter is modified based on the defect parameter.
Implementations of the invention may include one or more of the following features. Modifying the polishing parameter may include halting polishing of substrates from the cassette if the measured defect parameter is outside an acceptable range. The first substrate may be returned to the cassette, and the second substrate may be returned to the storage station. The first substrate may be a device wafer and the second substrate may be a monitor wafer. The first substrate may be transferred from the cleaner through the factory interface module to the defect monitor, and a defect parameter of the first substrate may be measured with the defect monitor. A third substrate may be transferred from the cassette through the factory interface module to a polisher, polished at the chemical mechanical polisher, and cleaned at the cleaner.
In another aspect, the invention is directed to a method of processing substrates in which a device substrate is transferred from a cassette through a factory interface module to a polisher, polished at a chemical mechanical polisher, cleaned at a cleaner, and transferred from the cleaner through the factory interface module to a defect monitor. A first defect parameter of the device is measured with the defect monitor. A monitor substrate is transferred from a storage station in the factory interface module to the polisher, polished at the polisher, cleaned at the cleaner, and transferred from the cleaner through the factory interface module to the defect monitor. A second defect parameter of the monitor substrate is measured with the defect monitor, and the first defect parameter is compared to the second defect parameter.
Potential advantages of the invention may include zero or more of the following. Particles and other defects on the wafer can be measured in-line by the polishing system, without significantly increasing the footprint of the system. Substrates can be stored in the factory automation interface unit, also without significantly increasing the footprint of the system. The stored wafers give the system more flexibility in scheduling wafer transport operations, thereby permitting throughput to be increased.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.